1. Field of the Invention.
The present invention relates generally to extension planks having interleaved rails and, more particularly, to a novel end cap for extension planks or the like.
2. Background Art.
An extension plank is a well known device which is used typically for providing an elevated work platform which may be supported between ladder jacks and frequently comprises two sets of a plurality of interleaved telescoping rails to provide variable length of the work platform. Extension planks of the type considered here are manufactured, for example, by A. W. Flint Company, New Haven, Conn. Such an extension plank may provide a work platform on the order of six to ten feet in length. For longer lengths, say on the order of eight to sixteen feet, a third set of interleaved rails may be provided for greater stability. In either case, the length of the extension plank is adjusted by longitudinally drawing the distal end of one set of rails away from the end(s) of the other set(s). The rails are typically constructed of wood, aluminum, or fiberglass.
So that the sets of rails may be so adjusted conveniently, the distal ends of the rails are attached together in spaced apart relation by end pieces so that all rails in that set will move together. Conventionally, the means for effecting this attachment have taken one of two forms. In one method, two strips of steel, or other suitable metal or material, are placed one on the top sides and one on the bottom sides of the ends of one rails of a set and the two strips are then riveted or otherwise connected through each rail so that the rails in that set are held apart by approximately the width of the rail and are secured for common movement relative to the other set(s) of rails. In the other method, a metal end cap or channel with open sides, formed of aluminum, for example, may be used to provide the top and bottom members while also covering the ends of the rails. The rails are held in place, as above, by rivets or other fasteners extending between the top and bottom members and through the ends of the rails.
The two conventional structures have the disadvantage of requiring the steps of cutting the metal end pieces to the necessary length and then forming the holes, by means of drilling or punching, to accommodate the fasteners. Additionally, both conventional structures present sharp metal corners which must be ground off in a further manufacturing step. These steps contribute a significant labor cost increment to the final product. Also, an important safety feature, that of a maximum-load warning label adhesively applied to the end piece and/or one or more rails, may be destroyed by weathering, exposure to water or chemicals, covering with paint, and/or vandalism.
Accordingly, it is a principal object of the present invention to provide an end cap for an extension plank or the like which presents no sharp corners requiring grinding during the manufacture of the plank.
Another object of the invention is to provide such an end cap that does not require a separate manufacturing step to form holes for fasteners.
An additional object of the invention is to provide such an end cap that does not require a cutting step during manufacture.
A further object of the invention is to provide such an end cap which may incorporate a maximum-load safety warning as an integral part thereof.
Yet another object of the invention is to provide such an end cap which is simply and economically manufactured.
Other objects of the invention, as well as particular features and advantages thereof will, in part, be obvious and will, in part, be apparent from the following description and the accompanying drawing figures.